Soldering fluxes

ABSTRACT

A METHOD OF SOLDERING OR TINNING IN WHICH THE FLUX USED CONSISTS OF OR CONTAINS A HYDROHALIDE, OTHER THAN A HYDROIODIDE, OF A MONOBASIC AMINO ACID OR OF AN ESTER OF SUCH ACID WITH AN ALCOHOL CONTAINING 1 TO 10 CARBON ATOMS.

United States Patent 3,748,191 SGLDERING FLUXES Rudolf Siegfried Straussand Peter David Teitz, London, England, assimiors to Frys MetalsLimited, London, England No Drawing. Original application Aug. 8, 1969,Ser. No. 848,701. Divided and this application Jan. 6, 1972, Ser. No.215,931

Int. Cl. 3231!; 35/34; C07c 143/00 US. Cl. 148-23 15 Claims ABSTRACT OFTE DISCLOSURE A method of soldering or tinning in which the flux usedconsists of or contains a hydrohalide, other than a hydroiodide, of amonobasic amino acid or of an ester of such acid with an alcoholcontaining 1 to 10 carbon atoms.

This is a divisional of copending application Ser. No. 848,701, filedAug. 8, 1969.

The present invention provides soldering and tinning fluxes based onmonobasic amino acids or esters of such acids with straight or branchedchain alcohols containing 1 to 10 carbon atoms, which we have found tocombine good fluxing power on copper and its alloys, tinplate, and steelwith a relatively low corrosive action of the flux residue which is leftafter soldering.

The soldering flux according to the invention consists of or contains ahydrohalide (other than a hydroiodide) of a monobasic amino acid. Thehydrohalide is preferably a hydrobromide. The flux may contain a mixtureof two or more such hydrohalides of monobasic amino acids or a halide ofa substance which contains a significant proportion of one or moremonobasic amino acids such as a protein concentrate derived fromhydrocarbon oils, or a fish or animal protein concentrate. Preferablythe amino acid contains not more than twelve carbon atoms.

If desired, the hydrohalide of the monobasic amino acid may be repaced,wholly or in part, by a hydrohalide of an ester of such an acid with analcohol, straight or branched chain, containing 1 to 10 carbon atoms.

Specific examples of suitable flux constituents are the hydrochloridesand hydrobromides of a-amino butyric acid, a-v-diamino butyric acid,leucine, isoleucine, valine, glycine, a-alanine, fl-alanine, phenylalanine, serine and lysine.

The active material, i.e. the hydrohalide of a monobasic amino acid orits ester may be used, as such, as the flux, e.g. in pure crystallineform; in solution in a suitable solvent, e.g. water, an alcohol, amixture of water and an alcohol, glycerine, ethylene glycol orpolyethylene gycol; in solution or dispersed in a suitable solid orsemi-solid medium such as polyethylene glycol of high molecular weightor rosin; or emulsified as an aqueous solution in mineral oil, a greaseor a wax. If desired suitable wetting agents or thickeners may beincluded in the flux when it is formulated as a solution or dispersion.

The active material may also be utilized in the form of a thickenedsolution or of a suspension as the flux portion of solder cream, bywhich is meant a suspension of finely powdered solder in the flux. Itmay also be used, in solid form or as a solution or dispersion in asuitable carrier, as a flux core in a solder wire, or as a flux coatingon solder wire, solder foil or tape, a solder pre-form or solder powder.

When the flux is an aqueous solution of the active material and isintended for use in oven-soldering operations it is desirable to includein the flux polyethylene glycol having a molecular weight of 200-1000.Preferably the polyethylene glycol is present in an amount of onequarter to twice the weight of the hydrohalide of a monobasic amino acidor its ester.

When the flux is to be used with higher melting grades of soft-solder orfor prolonged stoving in oven-soldering operations, it may contain asubstituted ammonium halide, other than an iodide, such for example asisopropylamine hydrobromide or ethylamine hydrobromide. The substitutedammonium halide is preferably present in an amount of quarter to twicethe weight of the hydrohalide of a monobasic amino acid or its ester.

When the flux is an aqueous solution a substituted ammonium halide maybe incorporated in addition to polyethylene glycol.

Fluxes according to the invention may be applied as a pre-coating to ametal surface, e.g. of copper, copper alloy or mild steel, which issubsequently to be soldered or tinned. In this case the flux is bestapplied to the metal surface as a solution in a volatile solvent. Atypical example of such solution is a 5-25% w./vol. solution of valinehydrobromide in isopropyl alcohol. Application of the coating solutionmay be carried out by dipping, brushing, roller coating, spraying or anyother suitable method. After application the coating is dried in air,preferably warm air. Metal surfaces so pre-coated can be soldered ortinned without further application of flux.

When the flux is an aqueous solution it is desirable, as is well known,to include in the solution a wetting agent in an amount of up to 1%w./vol. (i.e. gms. per cc.) to improve penetration of the flux into thejoint to be soldered. Any convenient wetting agent can be used for thepurpose, for example the long chain sulphonic acid sold under theRegistered Trademark Teepol.

The following are typical examples of fluxes for use in accordance withthe invention:

(a) Examples of hydrochlorides and hydrofluorides of monobasic aminoacids (i) a 5% w./vol. solution of valine hydrofluoride in water (ii) a5% w./vol. solution of alanine in water (iii) a 10% w./vol. solution oflysine hydrochloride in water (iv) a 10% w./vol. solution of valine inwater (v) a 5% w./vol. solution of alanine in water (vi) a 10% w./vol.solution of phenylalanine in water (vii) a 10% w./vol. solution ofleucine in water (b) Hydrobromides of monobasic amino acids (1') a 10%w./vol. solution of valine hydrobromide in water (ii) a 10% w./vol.solution of valine hydrobromide in isopropyl alcohol (iii) a 10% w./vol.solution of valine hydrobromide in equal volumes of water and isopropylalcohol (iv) a 10% w./vol. solution of ,B-alanine hydrobromide in water(v) a 10% W./VOl. solution of a-alaine hydrobromide in equal volumes ofwater and isopropyl alcohol (0) Hydrohalide' esters of monobasic aminoacids (i) hydrobromide of alanine ethyl ester (ii) hydrobromide ofalanine propyl ester (iii) hydrobromide of alanine iso-octyl ester (iv)hydrobromide of valine ethyl ester (v) hydrobromide of valine propylester (vi) hydrobromide of valine iso-octyl ester used as such or as a5-20% w./vol. solution in water or in isopropyl alcohol.

(d) Fluxes containing polyethylene glycol and/or a substituted ammoniumhalide (i) an aqueous solution containing 5% w./vol. fl-alaninehydrobromide and 3% w./vol. polyethylene glycol of molecular weight 200.

(ii) an aqueous solution containing 5% w./ vol. of valine hydrobromideand 3% w./vo1. isopropylamine hydrobromide.

(iii) an aqueous solution containing 5% W./sl. 8-

alanine hydrobromide and w./vol. isopropylamine hydrochloride.

(iv) an aqueous solution containing 5% w./vol. ,8- alanine hydrobromideand 5% W./vol. ethylamine hydrobromide.

(v) an aqueous solution containing 5% w./vol. 8- alanine hydrobromide,5% w./vol. ethylamine hydrobromide and 5% w./vol. polyethylene glycol ofmolecular weight 200.

When a component, such for example as a motor car radiator, is solderedin an oven flux and solder are applied to the joints to be solderedbefore introduction of the components into the oven. It is necessarythat the flux should have a sufiiciently long life to ensure that itwill not have evaporated and will remain active when the component hasattained within the oven a temperature suflicient to melt the solder.

Fluxes for use in accordance with the invention have been tested asfollows to determine the life of the flux:

Two drops of the flux, as an aqueous solution, are placed on a piece ofcopper sheet measuring 1% x 1%" and of thickness 0.01" which is thenheated to 120 C. to drive ofi all or most of the Water. The piece ofcopper is then floated on a bath of solder maintained at a temperatureof 390 C. for a trial time of 30 secs, after which a pellet of solder,consisting of 60% by weight tin and 40% by weight lead and weighing 0.12gm., is applied to the copper. If the solder spreads as it melts theflux has remained active. The test is continued with progressiveincrease in the trial time until it is found that the flux is no longeractive. The high temperature life of the flux is the maximum time lapseafter which the solder will still spread and wet the copper surface.

The following are the high temperature lives of certain of theabove-described fluxes as determined by this test:

High temperature Flux: life, seconds (1) w./vol. solution of fi-alaninehydrobromide in water 45 (2) Aqueous solution containing 5% w./vo1. ,8-

alanine hydrobromide and 5% w./vol. ethyl amine hydrobromide (3) Aqueoussolution containing 5% w./'vol. fl

alanine hydrobromide and 5% w./vol. isopropylamine hydrobromide (4)Aqueous solution containing 5% w./vol. B- alanine hydrohromide and 5%W./v0l. isopropylamine hydrochloride (5) Aqueous solution containing 5%w. vol. ethylalanine hydrobromide, 5% w./vol. ethylamine hydrobromideand 5% w./vol. polyethylene glycol of molecular weight 200 N (6) Aqueoussolution containing 5% w./vo1. valine hydrobromide, 5% W./vol.isopropylamine hydrobromide and 5% w./ vol. polyethylene glycol ofmolecular weight 200 120 What we claim as our invention and desire tosecure by Letters Patent is:

1. A soldering or tinning flux, which contains as its active ingredienta hydrobromide selected from the group consisting of hydrobromides ofvaline, a-alanine and B- alanine.

2. A flux as claimed in claim 1, which comprises a solution of saidhydrohromide.

3. A flux as claimed in claim 1, which comprises a dispersion of saidhydrobromide.

4. A flux as claimed in claim 2, which comprises an aqueous solution ofsaid hydrobromide.

5. A flux as claimed in claim 4, wherein said solution contains apolyethylene glycol having a molecular Weight of 2001,000.

6. A flux as claimed in claim 5, wherein said poly ethylene glycol ispresent in the solution in an amount ranging from about one quarter toabout twice the weight of said hydrobromide.

7. A flux as claimed in claim 4, wherein said solution contains asubstituted ammonium halide other than an iodide.

8. A flux as claimed in claim 5, wherein said solution contains asubstituted ammonium halide other than an iodide.

9. A flux as claimed in claim 7, wherein the substituted ammonium halideis present in the solution in an amount ranging from about one quarterto about twice the weight of said hydrobromide.

10. A flux as claimed in claim 7, wherein said substituted ammoniumhalide is selected from the group consisting of isopropylaminehydrobromide, ethylamine hydrobromide, isopropylamine hydrochloride andethylamine hydrochloride.

11. A flux as claimed in claim 2, which comprises a solution of saidhydrobromide in isopropyl alcohol.

12. A flux as claimed in claim 11, which comprises a 5-25% w./vol.solution of valine hydrobromide in iso propyl alcohol.

13. A solder cream, comprising a suspension of finely divided solder ina dispersion of a hydrobromide selected from the group consisting ofhydrobromides of valine, aalanine and ,B-alanine.

14. A solder wire having a core comprising a flux containing as itsactive ingredient a hydrobromide selected from the group consisting ofhydrobromides of valine, ozalanine and ,B-alanine.

15. Solder having a precoating of a flux containing as its activeingredient a hydrobromide selected from the group consisting ofhydrobromides of valine, a-alanine and p-alanine.

References Cited UNITED STATES PATENTS 2,470,957 5/1949 Strader 148-233,436,278 4/1969 Poliak 14823 3,406,285 10/ 1968 Scorgie 148-233,575,738 4/1971 Becker 14823 2,978,369 4/1961 Battle 148-23 3,127,2903/1964 Konig 14823 2,803,572 8/1957 Konig l4823 2,715,084 8/1955 Konig14823 3,675,307 7/ 1972 Strauss 14823 L. DEWAYNE RUTLEDGE, PrimaryExaminer P. D. ROSENBERG, Assistant Examiner U.S. Cl. X.R. 260-543

